This disclosure relates to a display including a thin film transistor using an oxide semiconductor, and to an electronic unit including the display.
In an active drive liquid crystal display or an active drive organic EL display, a thin film transistor is used as a drive device, and a charge corresponding to a signal voltage for writing an image is retained in a retention capacity. However, if a parasitic capacity generated in an intersected region between a gate electrode and a source electrode or a drain electrode of the thin film transistor is increased, the signal voltage is varied, thereby resulting in image quality deterioration.
In particular, in the organic EL display, when the parasitic capacity is large, the retention capacity is necessary to be increased, and thus a proportion of wirings and the like is increased in layout of pixels. As a result, probability of short circuit between wirings and the like is increased, thereby decreasing manufacturing yield.
Accordingly, in related art, as for a thin film transistor using oxide semiconductors such as zinc oxide (ZnO) and indium gallium zinc oxide (IGZO) for a channel, it has attempted to decrease a parasitic capacity formed in an intersected region between a gate electrode and a source electrode or a drain electrode.
For example, in Japanese Unexamined Patent Application Publication No. 2007-220817 and in “Self-aligned top-gate amorphous gallium indium zinc oxide thin film transistors”, J. Park, et al., Applied Physics Letters, American Institute of Physics, 2008, Vol. 93, 053501, there is disclosed a self-aligned top-gage thin film transistor in which a gate electrode and a gate insulating film are formed to have the same shape on a channel region of an oxide semiconductor thin film layer, and then a region not covered with the gate electrode and the gate insulating film of the oxide semiconductor thin film layer is reduced in resistance to form a source/drain region. In addition, in “Improved Amorphous In—Ga—Zn—O TFTs”, R. Hayashi, et al., SID 08 DIGEST, 2008, 42. 1, p. 621-624, there is disclosed a bottom gate thin film transistor having a self-aligned structure in which a source region and a drain region are formed on an oxide semiconductor film by backside exposure with use of a gate electrode as a mask.